I built this contact form for one website (my company’s) and at the time it was least expensive to just shoot out emails to a specific address with user’s messages and email addresses. Naturally, at one point I had to collect those emails & messages and use them so I ran into problem – what’s the easiest way to do that? Fortunately, our email server was GMail so I found a couple of ways to do it, avoid writing IMAP client and the easiest way for me was to use GMail’s built-in RSS feed and simply parse this feed to get what I want. In Cocoa, this should be simple enough but turned out not to be in my case.

Cocoa’s PubSub framework offers a nice way of subscribing to RSS feeds and it was ideal and simple for usage in this particular case. However, I just couldn’t get it to work with GMail’s authentication. I’ll explain below.

First I had to set up GMail account for easier access to the emails. Using search & filters, I found all emails that contained the info I needed and moved them to a separate temporary GMail label I created. At the same time I marked all emails as unread. This is very important because only unread emails appear in RSS feed and without this step, the feed for the label would appear empty.

Now the coding part. Ideally we would simply get PSClient and create a PSFeed, set username and password and traverse PSEntry objects in the feed. In theory, we’d do this:

PSClient *client = [PSClient applicationClient];
	NSURL    *url    = [NSURL URLWithString:@"https://mail.google.com/a/feed/atom/LABELNAME"];
	PSFeed   *feed   = [client feedWithURL:url];
 
	feed.login = txtEmail.stringValue;
	[feed setPassword:txtPass.stringValue];
 
	NSLog(@"Err: %@", feed.lastError);
 
	// Retrieve the entries as an unsorted enumerator
	NSEnumerator *entries = [feed entryEnumeratorSortedBy: nil];
	PSEntry *entry;
 
	// Go through each entry and get what we need
	while (entry = [entries nextObject]) {
		NSLog(@"%@", entry.summary.plainTextString);
	}

And this should work. However, it doesn’t. I always get this:

Err: Error Domain=NSURLErrorDomain Code=-1013 UserInfo=0x10017e450 "A username and password are required"

I still haven’t found the solution for this using PubSub framework. However I did manage to get the feed using plain HTTP NSConnection and simple authentication. So if anyone knows why this happens and/or knows how to solve it I would really appreciate if you notified me, thanks.

Anyway, back to our problem. Since this didn’t work, I simply tweaked it a bit and did a few things manually. I decided to use PSFeed’s initWithData:url: and pass the data (XML) manually from a NSTextField. First I opened the feed URL in my browser and logged in so I could actually see the feed. Then I opened the XML source of the feed and copied it to clipboard. Modified my GUI and added one more NSTextField which I used to paste XML feed data in and modified the Objective-C  Cocoa code like this:

	PSClient *client = [PSClient applicationClient];
	NSURL    *url    = [NSURL URLWithString:@"https://mail.google.com/mail/feed/atom/LABELNAME"];
	PSFeed   *feed   = [[[PSFeed alloc] initWithData:[txtInput.stringValue dataUsingEncoding:NSUTF8StringEncoding] URL:url] autorelease];
 
	feed.login = txtEmail.stringValue;
	[feed setPassword:txtPass.stringValue];
 
	NSLog(@"Err: %@", feed.lastError);
 
	// Retrieve the entries as an unsorted enumerator
	NSEnumerator *entries = [feed entryEnumeratorSortedBy: nil];
	PSEntry *entry;
 
	// Go through each entry and get what we need
	while (entry = [entries nextObject]) {
		NSLog(@"%@", entry.summary.plainTextString);
	}

And it finally worked fine. I parsed the feed manually and yeah, this isn’t exactly automated example but I did what I needed to do. And again, if anyone knows the solution to the authentication problem I’d love to hear it.